1. Field of the Invention
This invention relates to a printing apparatus capable of conducting a printing operation on the same size sheets which are supplied in either a longitudinal direction or in a lateral direction.
2. Description of Related Art
There has been conventionally known a printing apparatus in which the printing operation can be conducted on the same size sheets in both of the longitudinal and lateral directions. In the following description, the "longitudinal direction" for the printing operation does not correspond to the longitudinal direction of the sheet itself, but means that a sheet is supplied from a sheet cartridge to a printing unit in a direction which is parallel to the longitudinal direction of the sheet itself (the direction vertical to the shorter edges of the sheet, and parallel to the longer edges of the sheet), and the printing operation is carried out from the top line of the fed sheet at one shorter edge side of the sheet to the bottom line of the sheet at the other shorter edge side of the sheet. On the other hand, the "lateral direction" for the printing operation means that a sheet is supplied from a sheet cartridge to a printing unit in a direction which is transverse to the longitudinal direction of the sheet itself (the direction vertical to the longer edges of the sheet, and parallel to the shorter edges of the sheet), and the printing operation is carried out from the top line of the fed sheet at one longer edge side of the sheet to the bottom line of the sheet at the other longer edge side of the sheet.
For example, in order to print characters such as letters, symbols, images, etc. on an A-4 size sheet so that the character rows (lines) are directed in the longitudinal and lateral directions of the A4-size sheets (these print directions on the sheet and sheets on which the characters are printed in these print directions are hereinafter referred to as "longitudinal and lateral print directions" and "longitudinal and lateral sheets", respectively), such a printing device is so designed that two types of sheet cartridges, that is, a cartridge for A4-size longitudinal sheets (hereinafter referred to as "longitudinal sheet cartridge") and a cartridge for A4-size lateral sheets (lateral sheet cartridge) are detachably installed into the printing device. In this case, when a printing operation for sheets supplied in the longitudinal direction from the sheet cartridge is instructed, the sheets are supplied from the longitudinal sheet cartridge for A4-size sheets and then the printing operation is carried out. On the other hand, when a printing operation for sheets supplied in the lateral direction from the sheet cartridge is instructed, the sheets are supplied from the lateral sheet cartridge for A4-size sheets and then the printing operation is carried out.
In the apparatus capable of printing on sheets in the longitudinal and lateral directions as described above, when all sheets in the A4-size longitudinal sheet cartridge are used (that is, no sheet remains in the longitudinal sheet cartridge) during the printing operation for the sheets supplied from the A4-size longitudinal sheet cartridge, the subsequent printing operation cannot be conducted even when A4-size sheets having the same size remain in the lateral sheet cartridge. Therefore, the printing operation ceases, and sheets must be added to the empty A4-size longitudinal sheet cartridge to resume the printing operation.